not a rant but best stack answer i have read in a while:
http://stackoverflow.com/a/...

...This appears to work fine most of the time, but if the user enters invalid data enough times, the script will terminate with a RuntimeError: maximum recursion depth exceeded. You may think "no fool would make 1000 mistakes in a row", but you're underestimating the ingenuity of fools

I am Love the answer :)